FIVE DISCOVERY MISSION PROPOSALS
SELECTED FOR FEASIBILITY STUDIES

In the first step of a two-step process, NASA has selected
five proposals for detailed study as candidates for the next
missions in the Agency's Discovery Program of lower-cost, highly
focused scientific spacecraft.

In a unique step for this program, NASA has also decided to
fund a co-investigator to provide part of an instrument to study
the interaction between the solar wind and the atmosphere of Mars.
It is scheduled to fly aboard the European Space Agency's Mars
Express spacecraft in 2003. NASA plans to consider such
investigations, categorized as "Missions of Opportunity," in all
future Discovery and Explorer program Announcements of
Opportunity.

The mission proposals selected for further study would send
spacecraft to orbit Mercury, return samples of the two small moons
of Mars to Earth, study the interior of Jupiter, excavate and
study material from deep inside a comet nucleus and investigate
the middle atmosphere of Venus.

The five missions were among 26 full mission proposals
submitted to NASA. "The degree of innovation in these proposals
climbs higher each time we solicit ideas," said Dr. Ed Weiler,
acting associate administrator for space science at NASA
Headquarters. "Deciding which one or two of these exciting
finalists will be fully developed will be a very difficult choice
-- any one of them promises to return unique insights into our
Solar System. Meanwhile, the solar wind instrument will fill in
some critical gaps in our understanding of the history of water on
Mars."

Following detailed mission concept studies, which are due for
submission by March 31, 1999, NASA intends to select one or two of
the mission proposals in June 1999 for full development as the
seventh and possibly eighth Discovery Program flights.

The selected proposals were judged to have the best science
value among 30 total proposals submitted to NASA in response to
the Discovery Announcement of Opportunity (AO-98-OSS-04) issued on
March 31, 1998. Each will now receive $375,000 to conduct a four-
month implementation feasibility study focused on cost, management
and technical plans, including small business involvement and
educational outreach. As stated in the AO, the initial mission
cost estimates will not be allowed to grow by more than 20 percent
in the detailed final proposals.

The selected proposals are:

Aladdin, a mission to gather samples of the small Martian
moons Phobos and Deimos by firing projectiles into the moons'
surface and gathering the ejecta during slow flybys. It would
then return the samples to Earth for detailed study. Aladdin
would be led by Dr. Carle Pieters of Brown University in
Providence, RI, at a total mission cost to NASA, including
launch vehicle and operations, of $247.7 million.

Deep Impact, a flyby mission designed to fire an 1,100-pound
(500 kilogram) copper projectile into the comet P/Tempel 1,
excavating a large crater more than 65 feet (20 meters) deep,
in order to expose its pristine interior ice and rock. Deep
Impact would be led by Dr. Michael A'Hearn of the University of
Maryland, College Park, at a total cost of $203.8 million.

The Interior Structure and Internal Dynamical Evolution of
Jupiter, or INSIDE Jupiter, an orbiter spacecraft to study the
giant gas planet's interior, and its relationship to the
atmosphere, through intensive measurements of Jupiter's
gravitational and magnetic fields. INSIDE Jupiter would be led
by Dr. Edward Smith of NASA's Jet Propulsion Laboratory,
Pasadena, CA, at a total cost of $227.3 million.

The Mercury Surface, Space Environment, Geochemistry and
Ranging mission, or Messenger, an orbiter spacecraft carrying
seven instruments to globally image and study the closest
planet to the Sun. Messenger would be led by Dr. Sean Solomon
of the Carnegie Institution, Washington, DC, at a total cost of
$279.3 million.

The Venus Sounder for Planetary Exploration, or Vesper, an
orbiter with four instruments to measure the composition and
dynamic circulation of the middle atmosphere of Venus and its
similarities to processes in Earth's atmosphere. Vesper would
be led by Dr. Gordon Chin of NASA's Goddard Space Flight
Center, Greenbelt, MD, at a total cost of $195.8 million.

Aladdin and Messenger were finalists in the previous round of
Discovery Program mission selections in 1997.

The solar wind science hardware to be built as part of the
selected Mission of Opportunity is intended for an instrument
called the Analyzer of Space Plasmas and Energetic Atoms, or
ASPERA-3. The principal investigator for this instrument is Dr.
R. Lundin of the Swedish Institute of Space Physics in Kiruna,
Sweden. The co-investigator being funded by NASA is Dr. David
Winningham of the Southwest Research Institute, San Antonio, TX.
NASA will provide approximately $5.3 million for the electron and
ion spectrometer to be prepared for launch in 2003 aboard the Mars
Express mission.

The investigations proposed in response to this AO were
required to address the goals and objectives of the Office of
Space Science's Solar System Exploration theme, or the search for
extrasolar planetary systems element of the Astronomical Search
for Origins theme. The missions must be ready for launch no later
than Sept. 30, 2004, within the Discovery Program's development
cost cap of $190 million in Fiscal 1999 dollars over 36 months,
and a total mission cost of $299 million.

The next launch of a Discovery mission is scheduled for Feb.
6, 1999, when the Stardust mission will be sent on its way to
gather a sample of comet dust and return it to Earth in January
2006. The first Discovery mission, the Near Earth Asteroid
Rendezvous (NEAR) spacecraft, is due to arrive at its target
asteroid, 433 Eros, on Jan. 10, 1999, for at least a year of
close-up observations from an orbit around the Manhattan-sized
body.